Floor level tolerance for timber flooring in New Zealand
Three tolerances decide a good timber floor in New Zealand: how flat the subfloor is, how dry the subfloor and boards are, and how much room the floor gets to move. Get those right and the floor sits level, tight and quiet. Get them wrong and you see cupping, gaps and lifting.
The tolerances that actually matter
Timber flooring is an overlay: it goes on top of your subfloor, so the subfloor sets the standard. New Zealand building guidance and the relevant standards cover construction in general, but the numbers that decide your floor come from the manufacturer’s installation spec. Three do the heavy lifting: subfloor flatness, moisture, and the expansion gap around the edges. Our timber flooring installation guide sets out how a quality install handles all three, so confirm the exact figures for your floor with your installer and to the manufacturer’s installation spec.
Subfloor flatness
Flat is the one you can see and feel. Our installation guide works to a subfloor flat to within 3mm under a 3m straightedge before any boards go down: highs get ground back, hollows get filled. Skip it and the floor telegraphs every bump, with hollow spots underfoot, boards that rock, and gaps that open at the ends. Standards and manufacturers state flatness differently (often a few millimetres over 2m or 3m), so confirm the target for your floor to the manufacturer’s installation spec.
Moisture
Moisture is the number-one cause of floor failure, so it is the tolerance you cannot eyeball. On a concrete slab the moisture is measured (an in-situ probe or carbide reading) and the primer or barrier system is chosen off that reading, not by eye. On a timber subfloor, the boards and the subfloor should read within about 4% of each other before laying, and the timber is acclimatised flat, in its packs, in the actual room, for at least 48 hours. It is fair to ask to see the moisture and flatness readings taken for your job.
The tolerances at a glance
| What | Typical target | Why it matters |
|---|---|---|
| Subfloor flatness | Within 3mm under a 3m straightedge | Stops rocking, hollow spots and end gaps |
| Concrete slab moisture | Measured before laying; barrier chosen off the reading | Moisture is the top cause of floor failure |
| Timber subfloor moisture | Boards within about 4% of the subfloor | Boards settle without cupping or shrinking |
| Acclimatisation | 48 hours or more, flat, in the room | Timber reaches the room’s normal conditions first |
| Expansion gap | About 10mm in normal rooms, up to 14mm in humid spaces | Gives the floor room to move without lifting |
Figures follow Vienna Woods’ installation guide. Standards and manufacturers vary, so confirm the exact targets for your floor to the manufacturer’s installation spec and with your builder.
Board level and gaps: what is normal
A quality floor reads as one flat plane, with board end-joints staggered by at least 300mm and boards mixed across packs for a natural spread of colour and grain. A little seasonal movement is normal and not a fault: engineered oak takes on and gives off moisture with the seasons, so fine hairline gaps can appear in a dry winter and close again in humid months. What you should not see is a persistent step between boards, boards that lift or rock, or gaps that stay open year-round. Those point back to flatness, moisture or fixing, not the timber.
What happens when tolerances are missed
Hollow spots and end gaps
An out-of-flat subfloor leaves boards bridging the highs and hollows. You feel it as spring or rocking underfoot, hear it as a hollow tap, and see it as gaps opening at the board ends.
Cupping, lifting and movement
Trapped or excess moisture drives the board edges up above the centre. See why timber floors cup and how it is remedied, and what to do if your timber floor gets wet.
Common questions
What is the flatness tolerance for a timber floor subfloor in NZ?
Vienna Woods’ installation guide works to a subfloor flat to within 3mm under a 3m straightedge before laying. Standards and manufacturers state it differently, so confirm the target to the manufacturer’s installation spec.
What moisture level is acceptable before laying timber flooring?
On a concrete slab the moisture is measured and the barrier chosen off the reading. On a timber subfloor the boards should read within about 4% of the subfloor, and the timber is acclimatised in the room for 48 hours or more.
How much gap should a timber floor have around the edges?
An expansion gap of about 10mm in normal rooms, up to about 14mm in humid or high-swing spaces, hidden by the skirting or scotia, gives the floor room to move.
Are small gaps between boards normal?
Fine hairline gaps that open in a dry winter and close in humid months are normal seasonal movement. Persistent gaps, steps or lifting are not, and usually trace back to flatness, moisture or fixing.
Who is responsible for meeting the tolerances?
Your installer. A good installer tests and records subfloor flatness and moisture, acclimatises the timber, and designs in room to move. It is fair to ask to see the readings for your job. See our installation guide for the full method, or our timber flooring FAQ for more.
How a floor is laid
The full method, subfloor to finished edge, so you know what good looks like before you sign off.
Feel the boards first
Order free samples and see engineered European oak in your own light before you commit.
What it costs
See what a timber floor costs in New Zealand, from entry level to premium European oak.
Get it laid to spec, and talk to us first
The tolerances are the installer’s job, but the floor is our specialty. Order free samples, then get a quote for engineered European oak laid to spec.
